在占位符中查找控件

Question

我正在使用AJAX来创建一个用户控件，其中包含一个包含label和RadioButtonList或CheckBoxList的面板。 在.aspx页面中有一个占位符，该控件应该位于该位置。 我需要从占位符中找到List 我试过这个：

 public static int id = 1;
    QuestionPanelControl q1 ;

    protected void Page_Load(object sender, EventArgs e)
    {
       if (!Page.IsPostBack)
        {
           LoadQuestionPanelControl();
       }
    }

    //Next Button
    protected void Button1_Click(object sender, EventArgs e)
    { 
        id++;
        if (id <= 10)
        {
            //LoadQuestionPanelControl();
            PlaceHolder p = (PlaceHolder)Page.FindControl("PlaceHolder1");
            QuestionPanelControl c1 = (QuestionPanelControl)p.FindControl("QuestionPanelControl1");
           // QuestionPanelControl c1 = (QuestionPanelControl)p.FindControl("Panel_Question");
            RadioButtonList rb = c1.ChildRadioButtonList;
            if (rb.SelectedIndex == 0)
            {
                //DB 
            }
            else if (rb.SelectedIndex == 1)
            {
                //DB
            }
            else
            {
                Lsb_Unanswered.Items.Add("Question #" + id);
            }

            LoadQuestionPanelControl();

        }
    }

public void LoadQuestionPanelControl()
    {
        Session.Add("ID",id);
        q1= new QuestionPanelControl();
        q1.ID = "QuestionPanelControl1";
        Control c = Page.LoadControl("QuestionPanelControl.ascx");
        PlaceHolder1.Controls.Clear();
        PlaceHolder1.Controls.Add(c);

    }

当我使用断点时，我发现p的Controls属性为0。

注意：ChildRadioButtonList是QuestionPanelControl中的一个属性。 任何建议......

Answer 1

试试这段代码：

PlaceHolder p = (PlaceHolder)FindControlRecursive(Page, "PlaceHolder1");



public static Control FindControlRecursive(Control ctrl, string controlID)
{
 if (string.Compare(ctrl.ID, controlID, true) == 0)
 {
  // We found the control!
  return ctrl;
 }
 else
 {
  // Recurse through ctrl's Controls collections
  foreach (Control child in ctrl.Controls)
  {
   Control lookFor = FindControlRecursive(child, controlID);

   if (lookFor != null)
   return lookFor;  // We found the control
  }

 // If we reach here, control was not found
 return null;
 }
}

Answer 2

修改

   public void LoadQuestionPanelControl()
    {
        Session.Add("ID",id);
        Control c = Page.LoadControl("QuestionPanelControl.ascx");
        var q1= c as QuestionPanelControl;
        if(q1 != null)
        {
            q1.ID = "QuestionPanelControl1";

            PlaceHolder1.Controls.Clear();
            PlaceHolder1.Controls.Add(q1);
        }

    }

并查看占位符的Controls.Count是否为0以外的其他内容。